1. Field of the Invention
The present invention relates to an audio processing apparatus for receiving an at least one channel input signal and providing a plurality of user-defined effect and mixing functions for processing the input signal to generate an at least 3 channel output signal.
2. Description of Related Art
In the past it has been known in the art of audio processing to use so-called effect units for enriching the sound quality of an audio signal through the application of effects processing; i.e., the application of effects such as chorus, flange, delay, pitch shift, compression and distortion, among others; and for providing simulation of physical audio phenomena, such as speaker characteristics and room reverberation. FIG. 1 shows an exemplary use of a prior effect unit. Effect processor 10 receives input signal 12 from audio source 11a-c, typically input signal 12 is either a single channel; i.e., mono; signal or a two channel stereo signal from musical instrument 11a-b or audio mixer 11c. Effect unit 10 provides user definable analog and/or digital signal processing of input signal 12 and provides output signal 13, which is either a mono signal or a stereo signal, to amplifiers 14a-b or audio mixer 14c. Recently it has become standard to provide effect unit 10 with the functionality of several effects which the user; e.g., a musician; can arrange into a desired processing order; i.e., a user defined effects chain; thereby allowing the user to tailor the operation of effects unit 10 to achieve a desired audio result for output signal 13. As a particular example of the prior art, guitar systems have been known and used for years that provide guitar signal processing to simulate the characteristics of the tube guitar amplifier and speakers. With digital signal processing, currently available systems offer both the guitar signal processing (amplifier simulation) and effects processing. The systems of today lack any aspect of multi-dimensionality in the reproduction of the processed output. That is, all of the commercially available systems offer only stereo outputs which lack the requirements to offer a multi-dimensional reproduction of the sound. Custom system builders have built guitar systems for some of the professional touring guitarists with a three channel setup. Referring to FIG. 2, a diagram of the prior art three channel custom system is shown. These systems have typically been configured with amplifier stack 20 in the middle to reproduce the direct guitar signal. Typically the line output of direct guitar amp 21 is fed to the input of stereo effects processor 22. The output of stereo effects processor 22 is fed to stereo power amplifier 23 which powers two speaker cabinets 24a-b placed one on each side of direct guitar amplifier 21. In these systems the center channel will provide what is referred to as the dry guitar signal while the side speakers provide effect enhancement. For example, many of the stereo effects processors include echo algorithms where the echo will “ping-pong” between the two output channels and multi-voice chorus or pitch shifting algorithms. While these custom systems start to approach the potential of a multi-dimensional guitar audio processor they fall short in that there is not total flexibility for the user to define the location of the various effects within the three channel system. In summary, the prior art in this area lacks the ability to provide more than two output channels which are each derived from an at least one channel input signal and internally effected signals.
A second area of prior art related to the present invention is the commonly known surround sound audio system which has been finding wide application in the movie/home theater environment. FIG. 3 shows an exemplary surround sound system which includes audio signal source 31, which is typically recorded audio, for providing input signal 35 to surround decoder 30 and speakers 32a-c, 33a-b, 34 which receive dedicated signals from the outputs of decoder 30. Input signal 35 is typically a stereo signal, which may be encoded for surround playback, and decoder 30 processes the input signal to generate dedicated output channels for the left, center, and right front speakers 32a-c, the left and right rear; i.e. surround; speakers 33a-b and subwoofer 34. In one particular prior art surround sound decoder, the DC-1 Digital Controller available from Lexicon, Inc., additional signal processing is provided which simulates the reverberation characteristics of any of several predefined acoustic environments with fixed source and listening positions, where the source and listening positions are modeled as points in the simulated environment. The user/listener can then create the acoustic ambience of; e.g., a concert hall in a home listening environment. Limited user editing of environment parameters is also provided so that custom environments can be defined. The prior art in this area lacks multi-effect functionality/configurability and mixing functionality which would allow the user/listener to independently define the signal for each output channel in terms of input signal 35 and internally effected signals and is typically limited to stereo input signals from prerecorded audio sources. Additionally, this area of prior art lacks the flexibility of being able to vary source and listening positions in a simulated acoustic environment.